1. Field of the Invention
Among the best-known of insecticidal bacteria are the numerous strains of Bacillus thuringiensis (BT). The strains differ as to their insecticidal activity, as for example, the strain Kurstaki has killing activity against a number of (but not all) lepidopteran insects in the larval stages, while the Israelensis strains have potent toxicity against a variety of dipteran insects in the larval stages, including mosquitoes and blackflies. The bacterial toxin produced by the BT strain Kurstaki (BTK) has been extensively used as a commercial insecticide against crop pests, particularly the cole crops. In recent years, the Israelensis strain of BT (BTI) has been used to produce a commercial insecticide against mosquitoes.
While the naturally-occurring insecticides have numerous advantages over synthetic insecticides, they have not found extensive use because of the cost of products, due to the complex nutritional requirement of the host. It is therefore extremely desirable to provide improved endotoxins derived from the naturally-occurring endotoxins, which can be produced in more convenient hosts.
2. Description of the Prior Art
Schnepf and Whiteley, Proc. Natl. Acad. Sci. USA (1981) 78:2893-2897 describe the cloning and expression of the Bacillus thuringiensis crystal protein gene in Escherichia coli. Klier et al., The EMBO Journal (1982) 1:791-799 describe the cloning and expression of the crystal protein genes from Bacillus thuringiensis strain Berliner 1715. Held et al., Proc. Natl. Acad. Sci. USA (1982) 79:6065-6069 describe the cloning and localization of the lepidopteran protoxin gene of the Bacillus thuringiensis subsp. Kurstaki. Whiteley et al., describe cloning the crystal protein gene of B. thuringiensis in E. coli in Molecular Cloning and Gene Regulation in Bacilli, Academic Press, 1982, pages 131-144.
Wong et al., J. Biol. Chem. (1983) 258:1960-1967, describe the nucleotide sequence of the promoter region and part of the coding region from BTK HD-1-Dipel.
Milner, R. J., Identification of the Bacillus popilliae group of insect pathogens, pp. 49-59, and Singer, S., Potential of Bacillus sphaericus and related spore-forming bacteria for pest control, pp. 283-298, In Microbial Control of Pests and Plant Diseases, 1970-1980, ed. H. D. Burges, Academic Press, N.Y. 1981.